Time Division Duplex (TDD) wireless communication systems transmit and receive data on a single carrier frequency. Uplink (UL) and downlink (DL) transmissions are multiplexed by time slots within a fixed time interval. Different UL/DL ratios may be selected depending upon the degree of asymmetry in the DL and UL traffic rates. For a traditional homogeneous deployment of macro cells, the traffic patterns are relatively semi-static and the TDD UL/DL configuration, which defines the UL/DL time allocation, may remain unchanged for time intervals of at least hundreds of milliseconds or seconds. However, it has been observed that in heterogeneous deployment scenarios, such as networks consisting of small cells with or without a macro cell overlay, the UL and DL traffic patterns are more dynamic in nature. As such, system capacity may be significantly increased by adaptively reconfiguring the TDD UL/DL configuration in response to fast changes in UL and DL traffic patterns.
Another feature of traditional TDD systems is that cells within a geographical area may be configured with the same UL/DL configuration to avoid inter-cell UL-to-DL and DL-to-UL interference. When inter-cell UL-to-DL interference occurs, a UL transmission in one cell interferes with DL reception in a neighboring cell. When inter-cell DL-to-UL interference occurs, the DL transmission in one cell interferes with the UL reception in a different cell. Such inter-cell interference may occur both when the neighboring cells are operating on the same carrier frequency and when they are operating on different but adjacent carrier frequencies. If the UL/DL configuration in one cell is adaptively reconfigured based on intra-cell traffic patterns, then this change may cause severe co-channel and even adjacent channel interference to neighboring cells.